We propose to develop relatively atraumatic study methods that may be applied to patients for determining accurately and precisely measurements of local cerebral function in terms of absolute values of circulation and metabolism. By means of emission computed tomography of appropriately chosen radioactive indicators given intravenously, tracer distributions will be quantified with three-dimensional localization. Once validated, these methods will be applied to improve understanding of basic human cerebral physiology and will be evaluated for their usefulness in enhancing the diagnosis and management of patients with cerebrovascular disease, seizure disorders, and metabolic encephalopathies.